This invention relates generally to desiccant cartridges for use in receiver/dryers or accumulator canisters of automotive air conditioning systems. More specifically, it relates to a desiccant cartridge including a cup having an elongated center tube for replacing the fluid flow tube in a receiver/dryer or accumulator canister.
Desiccant cartridges containing desiccant particles are common in automotive air conditioning systems for dehydrating refrigerants. These desiccant cartridges are adapted to fit within receiver/dryer and accumulator canisters or assemblies.
Receiver/Dryer (R/D) and accumulator assemblies are used in automotive air conditioning assemblies to separate liquid refrigerant from gaseous refrigerant and to pass only the liquid downstream in the system. In many of these assemblies, a fluid flow tube is integrally formed with the top wall of the R/D or accumulator assembly and is commonly composed of metal such as stainless steel or aluminum.
Desiccant containing cartridges such as those shown in U.S. Pat. Nos. 5,814,136; 5,716,432; 5,685,087; 5,569,316; 5,540,348; 5,529,203; and 5,522,204 are disposed in the R/D and accumulator assemblies and function to dry the liquid refrigerant as it passes from the assembly inlet through the fluid flow tube to an outlet port contained in the structure. Typically, these cartridges contain a centrally disposed sleeve member that is adapted for snug reception over the fluid flow tube of the R/D or accumulator assembly so as to position the cartridge inside the assembly housing.
Some of the drawbacks to these R/D or accumulator metal fluid flow tubes are that they necessitate extra material, manufacturing, handling and assembly costs. Also, metal tubes can introduce contaminates into the air conditioning system in the form of metal chips and debris. As such, elimination of the metal tube could realize a significant cost savings and eliminate the risk of contamination.
Accordingly, there is a need in the art for the provision of a more economical structure which uses, as the fluid flow tube, a material that is less expensive than metal. An even more specific need is presented for the provision of a fluid flow tube that is integral with the desiccant containing cartridge.
Notably, the desiccant cartridge of the present invention is designed to eliminate the costly metal center tube by replacing it with a desiccant cartridge having a cup with an inner wall that defines an elongated center tube having first and second ends wherein the first end of the center tube communicates with the outlet port in the top wall of the R/D or accumulator assembly. The first end is formed from a plastic material, preferably a high temperature resistant plastic, to withstand the heat when the top wall of the R/D or accumulator assembly is welded to the canister-like housing. Also, it can be advantageous to use plastics, such as a plastic collar, having certain heat shrinkage properties so that the collar shrinks around the first end of the center tube and outlet port to form a better seal therebetween after the top wall of the canister is welded thereto.
In another aspect of the invention, the first end may be shaped to receive a high temperature o-ring, tubular insert, or ferrule, may be positioned within the first end of the center tube and outlet port to fill and seal the outlet port from the top wall of the R/D or accumulator and the center tube thereby further protecting and insulating the first end from heat during welding of the top wall of the R/D or accumulator onto the canister.
Accordingly, the center tube design of the desiccant cartridge provides a simple way for replacing a metal fluid flow tube while at the same time reducing the material, manufacturing, handling and assembly costs associated therewith.
Additionally, the plastic center tube of the desiccant cartridge further eliminates the metal chips and debris associated with metal tubes which can harm air conditioning systems.
The present invention provides a desiccant cartridge of the type including a cup having spaced inner and outer walls coaxially disposed wherein the inner wall defines an elongated center tube having first and second ends, and the outer wall has an upper and lower edge. The cup further includes a transverse portion having a top and bottom surface such that the transverse portion is connected to the outer and inner wall to define a chamber having an opening with the bottom surface of the transverse portion facing away from the chamber.
A plurality of desiccant particles is contained within the chamber for dehydrating air and refrigerants, and a cap having a planar portion with an inner circumference defining an aperture for slidably receiving the tube is securely received within the opening of the chamber to keep the desiccant particles contained therein.
In one embodiment, the cup has an elongated center tube with opposing first and second ends wherein the first end extends above the upper edge of the outer wall and the second end extends away from the bottom surface of the transverse portion. The cup is a one-piece plastic molding, preferably formed from polypropylene, by conventional molding techniques.
In another embodiment, the first end is formed from a high temperature resistant plastic, such as a polypropylene/nylon blend. In this embodiment, the first end is molded separately from the cup then press fit to the inner wall opposite the second end to form a center tube having a first end comprising a high temperature resistant plastic.
Accordingly, the desiccant cartridge of the present invention is designed to be used in combination with an R/D or accumulator canister including an outer wall axially disposed. The canister further has a bottom wall cooperating with the outer wall to define a chamber having an opening. The canister further is provided with a top wall having an outlet port therein, preferably centrally located. During assembly the top wall is secured, preferably by welding, to the canister opposite the bottom wall to seal the chamber.
Prior to placing and welding the top wall onto the canister to complete assembly of the R/D or accumulator, an assembled desiccant cartridge is placed within the chamber so that the second end of the tube communicates with a mounting flange that is spaced above the bottom wall of the receiver dryer to support the cartridge. When the top wall is placed onto the canister, the center tube aligns with the outlet port such that the first end of the tube is in communication therewith.
In either embodiment above, the first end may be shaped to receive a temperature resistant o-ring to further protect and insulate the first end from heat during welding of the top wall onto the canister.
Further, with respect to the center tube, and more specifically, the first end of the tube, it can be advantageous to use plastics, such as a plastic collar, around the first end of the tube which have heat shrinkage properties so that after heating of the tube during welding, shrinkage occurs during cooling so as to form a better seal between the center tube and the outlet port.
In yet another embodiment, the first end of the tube cooperates with a tubular insert to be able to communicate with the outlet port. In this embodiment, after the desiccant cartridge is placed into the R/D or accumulator canister and the top wall placed and secured thereon, the ferrule is inserted through the outlet port so that the insert sealingly engages with the first end of the tube and sealingly engages with the outlet port to fill an air gap therebetween allowing the center tube to communicate with the outlet port.
Accordingly, the elongated center tube configuration of the desiccant cartridge effectively eliminates the need for fluid flow tubes in R/Ds and accumulators. Instead, this fluid flow tube may be formed as a part of the desiccant cartridge itself.
Therefore, it may be appreciated that an object of the present invention is to provide a desiccant cartridge designed to eliminate the metal center tube used in R/D and accumulators while at the same time reducing the material, manufacturing, handling and assembly costs associated therewith.
It is a further object of present invention to provide a desiccant cartridge with an elongated center tube formed from plastic to eliminate the chips and metal debris associated with metal tubes which can harm air conditioning systems.
It is another object of the invention to provide a center tube having a first end comprising a high temperature plastic to withstand the heat from welding the top wall of the canister thereon.
Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings.